Aralkylcy anoforms



ia yl," tyli ary l kq ya et, fchloroar'yl radical, with, the provisof that -at least one t Y'andX? isan aryl, alkaryl alkoxyaryl, dimethylamin" I g aryl orchloroaryl radical an that the R, "R"'; Y-and Y: rad I of'18 carbonat'oms. I I "The aralkylcyanoforms' of"this invention have the un- 3,1665%?) 1 ARALKYLCYANQFORMS Elmore L. Martin and John K. Williams, Wilmington,

Del, 'assignors to E. I. du Pont de Nemours and orn- I pauy, Wilmington, Del., a corporation oi" Delaware No Drawing. Filed May'l, 1962, Ser. No. 191,449 6 Claims. (Cl. Zea-45s i This invention r elatesto organic compounds, having a plurality of cyano groups,that are useful in 'thermo- United States Pate graphic applications. More particularly, the invention relates to new compounds havingthreefcyano groups their preparation. n I I V I I Thermographic processes, i. e., processes flfor reproattached to a single carbon atom and to a'method for ducting writing, printing 'orother images by application of heat, are employed incertain systems of reproducing written records. Several types of compounds have been proposed for use in such processes and they have achieved varying degrees of success. T0 be of practical value in messes Patented Jan. 19, 1965 2 tures when in solution or in the molten form. This decomposition is illustrated by the equation;

It is the ability ofthe compounds of this invention to liberate cyanoform under controlled ',conditions that makes the compounds useful in thermo'graphic processes. The aralkylcyan'oformsj of this invention are prepared by reaction of cyanogen chloride or cyanogen fluoride 1 Witha substituted malononitrile of the formula wherein R, R", Y and Y have the meanings specified such processes, thethermogiaphic compositions should have a long shelf life, i.e,'they should be able' to be stored for long periods of time at ordinary storage temperatures without deterioration, andshould also'be capable of rapid .color development at the temperatures employed inthe 1 thermographic process Many of the presently known thermographic compositions are deficient in the range;

' between the temperature at which they-are stableand .the temperature. atWhicli color is'cleveloped. Therefore, :new compounds displaying improved th'errnographic characteristics iwou'ld constittuel valuable contributions 1 to.

It is an 'objectof invention to provide compounds ith the further proviso nesium and calcium compounds.

above, in the presence of an acid acceptor, e.g., a metal salt of the'substituted malononitrile, such as an alkali or alkaline earth metal salt. Thus, suitable acid acceptors I are, lithium, sodium, potassium, rubidium, cesium; mag- Sodium and potass1um are preferred smcejthey are readily available in the form of alkoxides and form salts with the aromatic substituted malononitriles. vThe alkali metals are generally'used as the alkoxides, although other alkali com I "poundsysu'ch :as" alkaliimetal fluorides," and hydrides, and alkaline earth compounds such ascalcium'oxide can alsojb'e employed O rg anic acid acceptors whichlcan usual and valuable characteristic of being (stable inythe;

solid form 15in; are; capable' 'of decomposing maa'fe efin "and free cyanoiorm-afstrong acid) at elevated te'mpera 'Thereactionlbetyv een I,

gen o f yvhich has an atomic umbef of 9, to l-;7,, inclusive,"'

is generally I he presencedoflani inert solvent or diluent.

nits-are,those thatare'inert to -the s each have a maximum be employed are thosiwhich are 'nonrreactive with jcyano gen halides but' vvhichl'reaetgvvithhydrogen fluoride or: a ,7

hydrogen chloride; e,g.,acetonitr;ile or: unsaturated hydro-I carbonssuch as borynle'ne and th'ejj faromat ic substituted .maioiibnitrii carried lout nd'er the reaction con oX ane an nhal bl d6 met le hlor d I o seth atfcan besepara d p oduc .by bv a' irat aralkylcyanoforrn I halide servesi as'thereaction medium.

lide and, substitut 'malonbnitrile in the the inert solvent or mmers: employed in -the reaction system;- tln-s'ome cases it' isidesirable to use a muchlarg eri exces s, e.g., 530x 10 times the theoretical molar equiva lennj'and in this'fcase theiexces's cyanogen sure to yield a,di-diniethylbenzylmalononitrile, B;

-; 1075631025 mm, in a yield amounting tb 7 v "Another m ethod for the preparation of aralliylinalonof nitrilesis illustrated by the followingjescripti'oriof the;

" I preparation of B-phenylethylmalononitrile startingwi tures. Reaction is essentially completed in times ranging from 5 minutes to an hour or more at temperatures ranging from -30 to 100 C. The exact time required depends on the particular reactants and operating temperatures employed. The reaction is conveniently carried out at atmospheric pressure, but subatmospheric and superatmospheric pressures are equally operable. Superatmospheric pressure is especially advantageous when the higher reaction temperatures, e.g., 75100 C., are employed and when low boiling reaction media are employed. With the most reactive substituted malononi triles the time of reaction can be controlled by the rate of addition of the cyanogen halide to the reaction system.

Cyanogen chloride is the preferred cyanogen halide reactant because of its ready availability. However, cyanogen fluoride can also be employed with satisfactory results.

The substituted malononitriles used a starting materials in the process of this invention can be prepared by known methods, such as thoseinvolving the reaction of a Grignard reagent with an alkylidene malononitrile in accordance with the following equation:

p v External' cooling is employedand the rate of addition of the hen-' zene solution is adjusted so that a reaction temperature lized from cyclohexane.

tral. The organic layer is separated and washed with aqueous sodium bicarbonate. After drying with anhydrou magnesium sulfate the filtrate is concentrated and the residue is distilled. There is obtained a 78% yield of ,B-phenylethylmalononitrile boiling at 109-ll0 C./0.2 mm. The compound solidifies on standing at room temperature and melts at 4446 C.

Analysis.-Calcd for C H N C, 77.62%; H, 5.92%; N, 16.46%. Found: C, 77.97%; H, 6.09%; N, 16.49%.

The products and process of this invention are illustrated in further detail in the following examples.

EXAMPLE I Preparation of u,a-dimethylbenzylcyanoform (1) NaH CH3 alid (CNN To a suspension of 4.8 g. (0.2 mole) of sodium hydride (9.6 g. of dispersion in oil) in 250 ml. of ether is added 36.8 g. (0.214 mole) of a,adimethylbenzylmalononitrile. The yellow suspension is stirred for 15 minutes and then 15 g. (0.24 mole) of cyanogen chloride is passed into the reaction mixture. The mixture is stirred for 15 minutes after the cyanogen chloride is added and the resulting solid that is formed (sodium chloride) is removed by filtration. The filtrate is concentrated to a volume of ml. and is then cooled in a bath of solid carbon dioxide and acetone. The solid that crystallizes is collected, washed with petroleum ether and recrystal- There is obtained 22.4 g. of u,m-dimethylbenzylcyanoform, M.P. -106 C. This product can also be named 1,l,1-tricyanor2-methyl-2 CoHa phenylpropane. A small sample is prepared for analysis by an additional crystallization from cyclohexane. This of 2530 C. is maintained during the addition of the re actants. After addition is completed, the resulting homogeneous solution is stirred undernitrogen at'45-48 C.

for 1 hour. At thefend of this time, the reaction mixture gives a positive test for Grignard reagent by the Michler ketone test; The thick reaction mixture is poured onto excess ice: and is carefully acidified by the addition of p 20% sulfuric acidffThe aqueous layer is separated. and

extracted'once with a mixture of ether and'benzene'. j The combined organic layers are washed twice With 'Watercontaining afew drops of dilute hydrochloric acid, then with two portions of saturated sodium chloride solution. C fAfte'r drying with anhydrous magnesium sulfate trate is concentrated"andf'distilled-under reduc monium hydroxide at 25 C. to form fi phenylethylcyanoacetamide. A mixture of "0.8 mole of B-phenyle'thylcy ano Analysis.Calcd for C H N C, 74.7%; H, 5.30%; 'N, 20.1%. Found; C, 73.9%.; 'H, 5.26%; N,'20.2%.

' 7 EXAMPLE i1 Preparation 0 13,-plzenylethylc yanoform fr-Phenylethylmalononitrile (17.0 g., 0.1. mole) is re- 1 acted with 2.4 g. .;(0. 1 mole) of sodium hydride in 100 ml. of tetrahydrofur'an at 0-5 C. Into the resulting solution is distilled 7.0}g'.- (0.114 mole ,of cyanogen chloride.

The resultingyellowneutral solution is concentrated under reduced pressure andiwater is added to the residue.

L The SQlidfj'fObfillIlCdf is stirred ,with 'asmall amount {of acetamide, sodium chloride and 1,2-diChloroetha'ne' is stirred at room temperature forj5 minute's and 'then 0.5" moleof phosphorus ox'ychljoride is added. The mixture is heated at reflux temperature with mechanical stirring for 8 hours; The reaction mixture is filtered'and the filter cake is washed with 1,2-dichloroethane. -"-Ice-water is added and the mixture is stirred to hydrolyzeexcess phosphorus QXYQhlOfldCn Solid sodium bicarbohate is added in small portions until the aqueous layer is neu- 5 water, filtered, and jwashed with cold water. The filter' cake *is dissolved in' ether and'thesolution is treated with decolorizing carbonfand anhydrous magnesium; sulfate. The filtered solution is'concentrated'to a volume of about .80 ml. and' cooled'first in ice andthen 'in." a mixture of s'olidfcarbon dioxide and acetone to ';6 0"C. There is a obtained 14- 'g. (72% oftheory) of colorless crystals of fi3 -phenylethyleyano form H (alternatively fnamed. I,1,1-tri-. cyano- 3 -phenylpropap6; ,M.Pl '47Q49Z'C. Cr ys'tallizaa tfion from ether doesin'ot change, the melting point.

v Foundz'C, 7.330%; H, 4.65%; N, 21.67%. These examples illustrate thepreparation of-two specific aralkylcyanoforms of thisinvention. However, the

invention includes any aralkylcya'noform of the formula Y have themeanings defined A-Methyl-A-phenylbenzyl- A-Stearylbenzylmalononitrile is mined-with a, dimethylbenaylhyanoform.Qn a

. whereupon it becomesdeep'blue. in lcolorij y, p a e lte (at the same temper" t 5 hereinbefore. Thus, when the process of the examples is repeated with a molar equivalent of the substituted malononitriles listed in the first column of Table I, replacing the a,a-dimethylbenzylmalononitrile of Example I, or the B-phenylethylmalononitrile of Example H, and reacted with at least one molar equivalent of cyanogen chloride or cyanogen fluoride there are obtained the 'aralkylcyanoforms listed in the second column of this table.

A-Benzylbenzylmalononitrile A-Benzylbenzyleyanoform. A-Methyl-A-phenylbenzylcynaoform.

A-Stearylbenzylcyanoform.

l-MethyLl-(A-naphthyl) -propylmalonom'trile.

l-Methyl-l-(A-naphthyl)-propylmalononitrile. cyanoform. AMethyl-A-ethyl-p-methyl- A-Methyl-A-ethyl-p-methylbenzylmalononitrile. benzylcyanoform.

1-Pheuy1-2-hexylmalouonitrile 1-(p-Methoxyphenyl)-2-phenylethylmalononitrile. V

1-Phenyl-2-hexyleyanoiorm. l-(p-Methoxyphenyl)-2-pl1eny1- ethylcyanoform.

The, productsof this invention possess the unexpected and valuable property of being stable in the solid state at temperatures up to their melting points.

hand, compounds of this invention when in solution, e.g.,

On the other the liberation of the strong acid on heating can be used "to develop a color. This is illustr'ated'in further detail as follows. A small sample of crystal violet lactone,

filter-paper. The piece of: Paper-containing these two com poundsis moistenje The hithe tof-known arylcyarioforms and aralkylcyano; V form sldo not decompose'in this way and thu'sar'je of no value inithermogra'p compositions, isfillu'strated a 'pieceof filter' paper; The'pa'per isfthen mois Rap .Th aralkycyano ms or this in v 'cally unsaturated monomer to be polymerized; The mixt'ureis then'zhea'ted to ,the" temperature at which theparx ticular artlltylcyanoform liberates c'ya'noformv iwhich ingj.

' 'i'the polymeriaation of .the unsaturated tened 'with"acetonearid'allo ed-vto dry in the are], The)? hen placed on a hot platej ,ention are alsouseful as cationic-polymerization initiators In this application,

' value as ingredients in thermographic compositions where H 'ith acetone and allowed todryi n "L 1 the eai'r'fi :The =filter-wpaper1 is:then placeds ona hot plate e' ma sa of xtfi ly b i 'lh m Y a QIma known 90m? Y "is a' 1 ber Selectedfrom' theqlass consistin 5 f I i allcoxyaryl, chloroaryl,

1 orms of'tl iisinyentionarealso us efiult s gredients oia thermal cell that isinertiat room.

' whereinv I -wherein 7 temperature, but develops a potential when heated near the melting point of the cyanoform. This is illustrated in further detail as follows: 7

On a hot plate whose temperature can be controlled within 1 C. of the desired temperature is placed a sheet of polytetrafiuoroethylene as an insulator, followed in succession by a copper slab making good electrical contact with a graphite slab (2 in. by 1% in.) forming the cathode, a mat of glass fibers on which is laid a magnesium sheet (3 in. by 2 in.) forming the anode, and finally another insulating sheet of polytetrafluoroethylene. The individual sections of the cell are maintained in good contact by 'u,a-dimethylbenzylcyanoform is dispersed in the center of the glass fiber mat and the cell is heated at a rate of about 1 C. per minute. During this heating, the voltage is observed as a function of temperature. It remains at zero until a' temperature of 118:1 C. is reached, at

' which point it rises to 0.98 volt (open circuit) in a period of about one-half minute. The voltage remains steady for about 3 4 minutes, then declinessteadily and reaches 0.1.4 voltin an additional ten minutes. In this particular assembly the voltage and temperature are simultaneously recorded on a twin channel recorder. The internal resistance of this; recorder is low enough (l0 ohms) so that the cell is 'in effect being continually discharged while what should be open-circuit voltage is being produced.

Under more favorable conditions, the true open-circuit voltag'ewould have been maintained for 30 minutes or more with intermittent discharging;

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that this invention is not limited to the specific embodiments thereof except-as defined in the appended claims.

The embodiments ofthe invention in which anexclu; f siv'e property or privilege is claimed as defined a'sffollows:

We claim:

' "LR' and R"are members selected from: tliefcla ss"con f 1 sisting o-f hydrogen, alkyl and" aryl,

' Yis' a 'inemberselected fromthe class consisting of ".hydrogen, aryl, alkary'l; alkoxyaryl, chloroaryl, "and dimethylaminoaryl,

hydrogen; alkyliaryl', alkaryl,

and dimethylaminoaryl,

7 than 18 carbonato'msjf p 2.- An aralkylcyanotorm compound of the formula providedthat atleastone of Y and Y is a memberI'se- I ,.lected'ffr. om the class consisting'of aryl,. alkaryl," 1 'alkoXy'aryl, ,dimejthylaininoaryland'chloroaryl,and I provided that .R', R"; Y, and Yv each'cont'ains not more -Y and R" are hydrogen, 5. a-Benzylbenzylcyanoform. R is alkyl, 6.fl-Phenylethylcyanoform. Y is alkoxyaryl, and V R and Y each contains not more than 18 carbon atoms. 5 3 a,a-Dimethylbenzylcanoform. 4. a-Methyl-p-dimethylaminobenzylcyanoform.

References Citedin tl ie file of this patent UNITED STATES PATENTS 2,995,597 Williams Aug. 8, 1961 

1. AN ARALKYLCYANOFORM COMPOUND OF THE FORMULA 